The module parameter "fwpostfix" is userspace controllable, unfiltered, and is used to define the firmware filename. b43_do_request_fw() populates ctx->errors[] on error, containing the firmware filename. b43err() parses its arguments as a format string. For systems with b43 hardware, this could lead to a uid-0 to ring-0 escalation.
Acknowledgements:
Red Hat would like to thank Kees Cook for reporting this issue.

Statement:
This issue does not affect the versions of the Linux kernel as shipped with Red Hat Enterprise Linux 5.
This issue does affect the versions of the Linux kernel as shipped with Red Hat Enterprise Linux 6, and Red Hat Enterprise MRG. Future updates for Red Hat Enterprise Linux 6 and Red Hat Enterprise MRG may address this issue.